Abstract: As the traditional channel estimation algorithms for MB-OFDM UWB system haven’t utilized the knowledge of channel length, the estimated channel length is always longer than the real one. To overcome the shortcoming, an improved channel estimation algorithm is proposed in this paper. The proposed algorithm exploits Least Squares (LS) technique for channel estimation and Signal Energy Estimation (SEE) to estimate the channel length. It effectively reduces the estimation dimensions of the signal subspace, and hence improves the estimation performance. Then the performance of the algorithms is analyzed. Finally, the performance of the algorithm and correctness of the analysis are proved by simulations.